1. Field of the Invention
The present invention relates to a working machine such as a compact excavator, which is provided with an exhaust path for releasing exhaust gas, which has been discharged from a muffler, to an outer side of a revolving upperstructure and makes use of a counterweight for the formation of the exhaust path.
2. Description of the Related Art
As a conventional technology of this kind, there is the technology disclosed in JP-A-2002-70077. This conventional technology is applied to a hydraulic excavator provided with a travel base, a revolving upperstructure mounted on the travel base, and working equipment attached pivotally in up and down directions to the revolving upperstructure and including a boom, an arm, and a bucket or the like. In this hydraulic excavator, an exhaust gas silencer for silencing exhaust gas discharged from an engine, that is, a muffler is accommodated in a recess formed in a counterweight. An exhaust pipe connected to the muffler, specifically a tailpipe is formed of a straight pipe extending in a vertical direction. An upper end portion of the tailpipe is inserted with a predetermined clearance in a guide pipe, in other words, an exhaust pipe that releases exhaust gas, which has been discharged from the tailpipe, to an outer side of the revolving upperstructure. The exhaust pipe in which the upper end portion of the tailpipe is inserted is provided in a vicinity of a lower end thereof with a flange, and this flange is fixed by bolts on a cover plate fixedly secured on the counterweight such that the above-mentioned recess of the counterweight is covered up. Exhaust gas from the engine is guided via the muffler and tailpipe into the exhaust pipe in which the tailpipe is inserted, and is then released from the exhaust pipe to an outer side of the revolving upperstructure.
According to the above-described conventional technology, intense heat of exhaust gas is transferred to the counterweight via the exhaust pipe in which the upper end portion of the tailpipe is inserted and also via the cover plate on which the exhaust pipe is fixed. The conventional technology, therefore, contributes to lowering the temperature of exhaust gas which is to be released to the outer side of the revolving upper structure. However, the conventional technology involves a problem in that sufficient heat transfer effect can be hardly obtained by the counterweight because the intense heat of the exhaust gas is conducted to the counterweight by way of the exhaust pipe and cover plate.
In this conventional technology, the intense heat of the exhaust gas guided to the exhaust pipe via the tailpipe is conducted to the cover plate that holds the exhaust pipe in place, and the thickness dimension of the cover plate is set small. There is, accordingly, a potential problem that the cover plate may undergo a deflection under the intense heat. If such a deflection occurs, a problem may arise in that the exhaust pipe held in place by the cover plate may lean to change the releasing direction of exhaust gas.